From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregory.clement@free-electrons.com (Gregory CLEMENT) Date: Fri, 08 Sep 2017 17:39:17 +0200 Subject: [PATCH] ARM: compressed: discard ksym/kcrctab input section In-Reply-To: <20170908153143.27279-1-ard.biesheuvel@linaro.org> (Ard Biesheuvel's message of "Fri, 8 Sep 2017 16:31:43 +0100") References: <20170908153143.27279-1-ard.biesheuvel@linaro.org> Message-ID: <8760ctryhm.fsf@free-electrons.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Ard, On ven., sept. 08 2017, Ard Biesheuvel wrote: > As it turns out, building the ARM kernel with EFI support pulls in > a couple of sections that we don't really need in the decompressor. > This is due to the fact the the UEFI stub uses sort() to sort the UEFI > memory map, which is an exported symbol pulled in from lib/sort.c. > > Before commit e4bae4d0b5f3 ("arm/efi: Split zImage code and data into > separate PE/COFF sections"), this resulted in the following layout > for the decompressor ELF binary. > > [Nr] Name Type Addr Off Size ES Flg Lk Inf Al > [ 0] NULL 00000000 000000 000000 00 0 0 0 > [ 1] .text PROGBITS 00000000 010000 009b3c 00 AX 0 0 512 > [ 2] .rodata PROGBITS 00009b3c 019b3c 001684 00 A 0 0 4 > [ 3] __ksymtab_strings PROGBITS 0000b1c0 01b1c0 000005 00 A 0 0 1 > [ 4] .data PROGBITS 0000b1c8 01b1c8 000020 00 WA 0 0 8 > [ 5] ___ksymtab+sort PROGBITS 0000b1e8 01b1e8 000008 00 WA 0 0 4 > [ 6] .piggydata PROGBITS 0000b1f0 01b1f0 77ac38 00 A 0 0 1 > [ 7] .got.plt PROGBITS 00785e28 795e28 00000c 04 WA 0 0 4 > [ 8] .got PROGBITS 00785e34 795e34 000028 00 WA 0 0 4 > [ 9] .pad PROGBITS 00785e5c 795e5c 000004 00 WA 0 0 1 > [10] .bss NOBITS 00785e60 795e60 00001c 00 WA 0 0 4 > [11] .stack NOBITS 00785e80 795e60 001000 00 WA 0 0 1 > > Commit e4bae4d0b5f3 made some changes to the linker script to allow the > UEFI firmware to map the decompressor with strict R-X/RW- permissions > before invoking it. Unfortunately, this turns out to break the boot on > some systems, because the linker now also moves the ksymtab/kcrctab > sections around, resulting in .piggydata to appear misaligned. > > [Nr] Name Type Addr Off Size ES Flg Lk Inf Al > [ 0] NULL 00000000 000000 000000 00 0 0 0 > [ 1] .text PROGBITS 00000000 010000 00a93c 00 AX 0 0 4096 > [ 2] .rodata PROGBITS 0000a93c 01a93c 001684 00 A 0 0 4 > [ 3] __ksymtab_strings PROGBITS 0000bfc0 01bfc0 000005 00 A 0 0 1 > [ 4] .piggydata PROGBITS 0000bfc5 01bfc5 77ac47 00 A 0 0 1 > [ 5] .got.plt PROGBITS 00786c0c 796c0c 00000c 04 WA 0 0 4 > [ 6] .got PROGBITS 00786c18 796c18 000028 00 WA 0 0 4 > [ 7] .pad PROGBITS 00786c40 796c40 000008 00 WA 0 0 1 > [ 8] .data PROGBITS 00787000 797000 000200 00 WA 0 0 4096 > [ 9] ___ksymtab+sort PROGBITS 00787200 797200 000008 00 WA 0 0 4 > [10] .bss NOBITS 00787208 797208 00001c 00 WA 0 0 4 > [11] .stack NOBITS 00787228 797208 001000 00 WA 0 0 1 > > So let's align piggydata explicitly, and discard these sections from the > binary. > > Cc: Russell King > Fixes: e4bae4d0b5f3 ("arm/efi: Split zImage code and data into separate ...") > Tested-by: Gregory CLEMENT Actually I had not tested a kernel with these two changes in the same time. But now I've just done it, and it still works, so the patch and my tested-by remain valid. Thanks! > Signed-off-by: Ard Biesheuvel > --- > arch/arm/boot/compressed/piggy.S | 1 + > arch/arm/boot/compressed/vmlinux.lds.S | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/arch/arm/boot/compressed/piggy.S b/arch/arm/boot/compressed/piggy.S > index f72088495f43..5d52c556dd32 100644 > --- a/arch/arm/boot/compressed/piggy.S > +++ b/arch/arm/boot/compressed/piggy.S > @@ -1,5 +1,6 @@ > .section .piggydata,#alloc > .globl input_data > + .align 2 > input_data: > .incbin "arch/arm/boot/compressed/piggy_data" > .globl input_data_end > diff --git a/arch/arm/boot/compressed/vmlinux.lds.S b/arch/arm/boot/compressed/vmlinux.lds.S > index 7a4c59154361..5c5265be4605 100644 > --- a/arch/arm/boot/compressed/vmlinux.lds.S > +++ b/arch/arm/boot/compressed/vmlinux.lds.S > @@ -29,6 +29,7 @@ SECTIONS > * of the text/got segments. > */ > *(.data) > + *(*ksymtab* *kcrctab*) > } > > . = TEXT_START; > -- > 2.11.0 > -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com